Transparency and refraction of lens depend directly on the integrity of the crystallin family proteins. Native form of these proteins can pack tightly at extremely high concentration, and yet effectively sustain short range interaction which may prevent proteins from aggregation. Modification of these proteins both at congenital and post-translational level can cause formation of inclusion in lens and ultimately lead to cataract. With an estimated 45 million cases of human blindness worldwide, detailed understanding of cataract formation becomes more urgent than ever. Two key questions related to cataract formation still remain to be answered: 1) what leads protein aggregate after modification, and 2) what happens when crystallins unfold. To address these questions, y-crystallin and its nature mutant, opj, will be used as the model system. yS differs from the rest of y-crystallin family proteins by locating at the water rich cortical region, whereas others mainly reside in the condensed region of the lens. In adult mammalian lens, yS is the most abundant protein replacing the expression of the rest of y-crystallins. Opj, an inherited cataract in mice, bears a single mutation from yS, exhibiting a marked, concentration-dependent decrease in protein solubility at close to physiological temperature. Despite of its importance, structural and dynamic information of yS and its mutant remain sparse. Nuclear magnetic resonance (NMR) spectroscopic and biophysical methods will be employed to study the structure and dynamics of the yS-crystallin lens protein and its nature mutant, opj. This proposal is intended to 1) reveal the structural difference between the intact and the mutated proteins, 2) study the difference in protein dynamics, and 3) characterize the formation of amyloid fibril by unfolded opj. The proposed project will help gain insights of the mechanism underlying how the mutated crystallin proteins can ultimately lead to cataract formation. Cataract continues to impose threats to human health with more than half million new cases every year in the USA and UK alone. Using the yS-crystallin and its nature mutant opj as model system, full understanding of the mechanism of cataract formation will provide rationales for development of new therapeutic alternatives as opposed to the conventional invasive surgical method. [unreadable] [unreadable] [unreadable]